1. Field of the Invention
The present invention relates to an apparatus for controlling exhaust noise in an internal combustion engine, in particular, in which a bypass pipe diverging from an exhaust pipe is composed of a U-shaped section and a reverse U-shaped section to minimize the installation space of the bypass pipe, and the length difference between the exhaust pipe and the bypass pipe is enlarged so that a noise in a low frequency band can be suitably controlled.
2. Description of the Related Art
In general, mufflers are used for restricting exhaust noise of the internal combustion engine such as engines of vehicles. However, the mufflers have a complicated structure so that pneumatic resistance of exhaust gas is increased while passing the muffler thereby increasing back pressure of the engines and thus reducing efficiency of the internal combustion engines.
Also, since exhaust noise of the vehicles has main components changing according to variation of engine rotation speed, it is difficult to manufacture a muffler which can be effectively operated across the overall rotation speed of an engine.
Meanwhile, in order to overcome disadvantages of the method for restricting exhaust noise by using the muffler, researches are being actively carried out about active control of exhaust noise as a new noise controlling method. As an example of typical methods about the active controlling method which are being currently researched, there is an apparatus for controlling exhaust noise by using a speaker in which noise is measured to judge data by using a noise measuring microphone installed in the exhaust pipe for allowing exhaust gas to pass through, in which the data are outputted through the speaker installed in the exhaust pipe which generates destructive sound having the same magnitude and the opposite phase as exhaust noise measured in the microphone to have a destructive interference with exhaust noise, which is a noise source, thereby reducing exhaust noise outwardly released from the vehicle.
However, there are problems that, in the method of generating destructive sound through the speaker installed in the exhaust pipe, a large magnitude of noise is generated from exhaust gas and the main components thereof are in a low frequency band so that the speaker is required to have very high output power to compensate noise and a large magnitude of diameter to generate low frequency sound as the features of the general speaker, whereas there are difficulties for manufacturing and maintaining the speaker in a large size and ensuring space for installation.
Meanwhile, as another example of active control, an apparatus for actively controlling a path difference in a pipe for transferring noise is disclosed in Korean Published Patent Gazette No. 10-1999-2473. The apparatus is provided with a bypass section in which a U-shaped bypass pipe 10 is attached to an exhaust pipe 1 for outwardly releasing exhaust gas of an engine 40 so that an exhaust gas outlet is bypassed into two branches and then combined into one again.
The bypass pipe 10 has fixed members 11 and 12 diverging from the exhaust pipe 1 and a movable member 14 slidingly coupled with the fixed members 11 and 12, in which the length of the bypass pipe 10 is actively varied by an actuator 20 having an actuator rod 20 for sliding the movable member 14 from the fixed members 11 and 12, and a control unit 30 for judging the operation of the actuator 20 if any to output a control signal based upon noise measured from the microphone 32 installed at one side of the exhaust pipe 1 and an rpm signal of the engine.
In such an apparatus for actively controlling noise by using the path difference in the noise transferring pipe, the length the bypass pipe 10 is adjusted so that noise has the phase difference of 180xc2x0 in passing the bypass pipe 10 and the exhaust pipe 1 thereby to mutually compensate exhaust noise passing the two pipes.
However, in the active noise controlling apparatus by using the path difference of the noise transferring pipe of the related art, the difference between the length a+b+c of the bypass pipe 10 diverging from the exhaust pipe 1 and the length of the exhaust pipe area where exhaust gas passes without flowing into the bypass pipe 10 should be large for compensating low frequency noise in considering that general exhaust noise is in the low frequency band. Accordingly, it is difficult to ensure a space for installing the bypass pipe 10 extended in the lower part of the vehicle and support the actuator 20 and the actuating rod 22 when sliding the movable member 14 in the fixed members 11 and 12 for varying the length of the bypass pipe 10 so that noise in the low frequency band may not be suitably controlled.
Also, hot exhaust gas passes through the bypass pipe 10, which causes a localized thermal deformation to the fixed members 11 and 12 or the movable member 14 thereby deteriorating the sliding operation and endurance of the movable member 14.
Further, when exhaust gas is bypassed into the bypass pipe 10, foreign materials can be introduced into the bypass pipe 10 together with hot exhaust gas so that the sliding operation of the movable member 14 can be obstructed.
The present invention is proposed to solve the foregoing problems of the related art, and it is therefore an object of the invention to provide an apparatus for controlling exhaust noise of an internal combustion engine in which a bypass pipe connected to an exhaust pipe is alternately provided with U-shaped and reverse U-shaped sections so that a space for installing the bypass pipe can be minimized and the variable length of the bypass pipe can be extended thereby reducing noise in a wide band.
It is another object of the invention to block introduction of foreign materials into the bypass pipe thereby preventing malfunction of the bypass pipe by the foreign materials.
It is further object of the invention to allow the bypass pipe to be varied in the length parallel to the exhaust pipe to reduce noise in the wide band while ensuring suitable installation of the bypass pipe.
According to an embodiment of the invention to obtain the foregoing objects, it is provided an apparatus for controlling exhaust gas in an internal combustion engine, comprising: an exhaust pipe for outwardly releasing exhaust gas from the engine; a bypass pipe variable in length which diverges from said exhaust pipe with a distance and has U-shaped and reverse U-shaped sections formed alternately; an actuator having an actuating rod connected to said bypass pipe to vary the length of said bypass pipe; and a control unit for controlling said actuator.
According to another embodiment of the invention to obtain the foregoing objects, it is provided an apparatus for controlling exhaust gas in an internal combustion engine, comprising: an exhaust pipe for outwardly releasing exhaust gas from the engine; a movable bypass pipe diverging from said exhaust pipe with a distance and arranged parallel to said exhaust pipe and variable along the length of said exhaust pipe; an actuator having an actuating rod connected to said bypass pipe to vary the length of said bypass pipe; and a control unit for controlling said actuator.
According to further another embodiment of the invention to obtain the foregoing objects, it is provided an apparatus for controlling exhaust gas in an internal combustion engine, comprising: an exhaust pipe for outwardly releasing exhaust gas from the engine; a main bypass pipe diverging from said exhaust pipe with a distance and having a variable length; an auxiliary bypass pipe diverging from said main bypass pipe with a distance and having a variable length; an actuator having an actuating rod connected to said bypass pipe to vary the length of said bypass pipe; and a control unit for controlling said actuator.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.